1. Field of the Invention
The present invention generally relates to computer software. More specifically, the present invention relates to computer software applications configured to facilitate the interactve design of three-dimensional (3D) models that include complex infrastructure configurations.
1. Description of the Related Art
Currently, computer aided design (CAD) applications are available that allow a designer or engineer to generate computer models of real-world 3D objects. Such models are generally based on the of real-world geometry of the object being modeled. Typically, a user interacting with the CAD application supplies a set of input data specifying various attributes or constraints for the object being modeled. The CAD application uses this data to generate a virtual representation of the object being modeled.
One common class of objects modeled using current CAD applications includes longitudinal structures, such as a roadway. Other examples of longitudinal structures that may be modeled include sidewalks, tunnels, dams, bridges, runways, pipelines, individual pipes, conduits, and the like.
A common feature of these real-world objects is that they may be modeled using a series of cross-sections. Within the 3D model, the cross-sections are placed sequentially along a central, longitudinal alignment. The alignment provides a path through the 3D model, and along the path the cross-sections specify the geometry of the structure. For example, a cross-section of a roadway could specify the geometry of road surface lanes and a curb and a gutter located on either side of the roadway. The geometry for the cross-section would be specified by input data such as the width and grade of the road, the height and width of the curbs, and other relevant data values. A CAD application typically generates the 3D model by extruding instances of various cross-sections along the central alignment. The 3D model of the longitudinal structure emerges as the cross-sections are extruded along the central alignment. The data for the completed model may then be used to generate a visual representation of the object, e.g., an onscreen display or a printed blueprint. Additionally, the completed 3D model may be used in a variety of other calculations. For example, the volume of concrete or asphalt required for a given road surface may be calculated.
Problems arise with this approach because current CAD applications generate a 3D model of these structures using a single longitudinal alignment. In reality, however, many real-world longitudinal structures intersect one another. For example, one road may include intersections with a number of other roads. This makes it difficult for a CAD application to generate an accurate 3D model of a complex infrastructure using a single alignment. Because there is only a single alignment representing a main roadway, for example, there is no alignment to position cross-sections representing the intersecting road.
One approach to modeling complex infrastructure configurations has been to generate a different 3D model for each longitudinal alignment. For example, a CAD application may be used to generate a separate 3D model for each of two roads that intersect one another. Integrating the individual 3D models resulting from this approach has proven to be difficult, however. First, because the intersecting regions of an alignment may be included in both 3D models, any engineering calculations using these models may become inaccurate. For example, calculating the volume of concrete or asphalt needed for an intersection may be doubled by such an approach, as the intersection is included in both alignments. Second, intersecting alignments are often much more complicated than a simple crossover point of two longitudinal alignments. For example, a small two-lane residential road may intersect with a larger multi-lane thoroughfare. In such a case, the characteristics of the thoroughfare (e.g., slope, grade, position, materials) dominate the characteristics of the intersection. Thus, even though being modeled separately, the model for the residential road must incorporate substantial elements that are more accurately associated with the larger thoroughfare.
Another approach has been to selectively omit sections of the infrastructure being modeled from one of the two intersecting alignments. This allows for more accurate engineering calculations, but ignores one of the reasons for using a CAD application—to develop a representation of the real world structure that models the totality thereof. Moreover, building a number of individual alignments in separate models can quickly become unwieldy.
Accordingly, there remains a need for an improved CAD application configured to model complex infrastructure configurations, in general, and for a CAD application that can effectively model infrastructures that include one or more longitudinal alignments, in particular.